In the optical arts various systems for correcting the optical aberrations shown both by natural lenses such as the human eye and by artificial lenses such as photographic lenses and the like, are very well known. However, such systems generally comprise the superposition, to the defective lens, of an additional lens or of a series of additional lenses suitably designed and calculated to the effect that, by means of the joint and complementary action of said lenses with the defective lens, the defects presented by the latter by corrected.
Thus, according to the traditional optical arts, spherical aberrations of lenses are corrected by means of the addition of various elements that jointly refract the light such that the same will be directed in the adequate directions in order to avoid sphericity of the images projected or observed through said lenses. The aberrations of the chromatic type, also, are normally corrected by the superposition of lenses correcting the polychromatic refraction caused by the prisms constituted particularly at the peripheries of common lenses or in the lenses having a small curvature radius.
Other type of aberrations, known as astigmatism, farsightedness or presbyopsia, myopic astigmatism and the like, also constituting common diseases of the human eye, are corrected in accordance with the prior art, by means of lenses suitably designed to compensate the deficient refraction of the light rays produced by defects either in the cornea or in the crystalline of the eye.
One other known method of correcting said aberrations, is to provide a relatively large lens partially covered by a diaphragm which masks a large proportion of the peripheral area of said lens and leaves as the only useful part thereof just a small area at the center of the lens, wherein the parallelism of the faces is greater and therefore the formation of peripheral prisms is suitable masked.
However, the first above mentioned technique of adding correcting lenses is highly costly and requires very accurate calculations, whereby the correcting lenses normally result of a high price and, in the second of the above mentioned techniques, the said techniques may be considered as a very primitive remedy to the problem, which does not take advantage of the major part of the area of the lens and does not correct, but only avoids the utilization of the more critical areas of said lens, whereby said prior art techniques of correcting optical aberrations, have left much to desire.
One other method of partially correcting optical aberrations are the non-refracting devices such as the so called stenopeic spectacles which have been known as a visual aid from early times. For instance, in the text book System of Ophthalmology, by Sir Steward Duke-Elder and David Abrams, edited by Sir Stewart Duke-Elder, Volume V, pages 794 et seq, it is very clearly mentioned that said stenopeic spectacles where advocated and their optical principles explained by Daza de Valdes in 1623, and were first employed clinically by the French ophthalmologists Serre in 1857 and Frans Donders in 1864. However, as also clearly stated in said text book, the main disadvantage of a stenopeic hole is that it provides a very small visual field and, since it does not move with the eye, it is of little advantage to the wearer when walking about. It is also mentioned in said text book that when it is required for general purposes a disc composed of several such openings bored in a sheet of opaque material may prove "better than nothing", which means that said stenopeic spectacles have proven to be highly inefficient articles and, as is also well known and mentioned and described in many optics books, a stenopeic hole has as its sole purpose to avoid the entrance into the defective eye or lens of the diffraction circles that generally accompany pure light rays, whereby said stenopeic holes must be obviously of circular shape, and as Duke-Elder et al very clearly mention in their text book, in order to be effective, the multiplicity of stenopeic holes provided in spectacles, must be spaced in about 4 mm between each other, and must have a size of about 1.5 mm for distant vision and 0.3 mm for near vision.
The fact that the stenopeic holes have as their only purpose to prevent the entrance of the diffraction circles, whereby their form must be obviously circular, and the fact that the spacement thereof must be relatively large in stenopeic spectacles, render said stenopeic spectacles as highly impractical devices for general use, inasmuch as the effort of the wearer is not compensated by the benefit produced by the improvement of the image perception, and thus said stenopeic spectacles have not gained throughout such a long time any acceptance among the general public, regardless of the fact that many persons may be in real need of something more than mere spectacles or mere contact lenses to improve their vision. The problems encountered with the decrease in the perception of light intensity and vision angle with the stenopeic holes, is of considerable importance and has been determinant of the lack of acceptance for these devices among the public.
The stenopeic spectacles were improved by Guthrie, who provided a surface covered by stenopeic holes of the size and with the spacement mentioned above, with an additional centrally arranged so called stenopeic slit, in order to increase vision at least when reading, but the stenopeic, slit may be regarded as highly inefficient for many particular purposes, and more particularly when the defects in the eye to which the said stenopeic slit is superposed, include aberrations of the spherical type and more particularly astigmatism.
In Mexican Pat. No. 132,553 patented Feb. 10, 1976 to the same applicant hereof, an optical grid is described for causing interference of light rays and which to a great extent remedied the defects of the devices of the above described techniques, including the stenopeic spectacles.
Said grids were designed for application to spectacles and comprised an undetermined number of square openings, said grids being either flat or concave to be adapted to the rings of ophthalmic frames for spectacles with conventional glasses and/or in substitution thereof.
Even when the optical grid of Mexican Pat. No. 132,553 is very efficient to correct optical aberrations particularly caused by the excess of luminosity, by means of a process of light interference effected through the plurality of square holes that it contains, said grid does not provide any usefulness in the correction of optical aberrations of other types and, of course, said optical grid is mainly based in the decrease of the light intensity by means of said interference, thus causing obscurity or lower intensity of the light detected, with a better perception of the images. However, the considerable decrease of luminosity produced by the grids of Mexican Pat. No. 132,553 is in itself an inconvenience, in view of the fact that particularly in dark places or in the twilight time of the day, as well as in the darkness of the night, the use of said grids causes a loss of visual intensity which is not compensated by the improvement of the image perception, and this may cause the loss of perception of many dark objects.
The principle of providing square holes uniformly spaced from each other, however, as described in said Mexican Pat. No. 132,553, for the first time changes the concept of using stenopeic holes for trying to improve visual perception, and may be regarded as a considerable improvement in the art of correcting optical aberrations of lenses. However, this grid was very primitive and may be regarded as a first effort of applicant to provide a practical device that could be used in substitution of glasses for spectacles, without the loss of light intensity and however with a high improvement in the image perception and an absolute correction of optical aberrations as will be described in the instant application.
Therefore, with the exception of the optical grid described and claimed by applicant in Mexican Pat. No. 132,553, which may be regarded as a considerable improvement over the prior art, all other prior art devices were absolutely impractical and, as very clearly described by Stewart Duke-Elder, may be regarded just as something which is "better than nothing".